On Sun, Aug 16, 2009 at 6:51 AM, Niels Mayer<nielsma...@gmail.com> wrote: > Executive summary: seems like big announcements of "provably correct > software" would be easier to achieve in Java+Clojure than for C/Haskell used > in the current "big news" regarding a provably secure kernel. However, given > the bugs I enountered in a java-based DVR contract-from-hell that was a > deadlocking side-effecting nightmare, I think this kind of "provability" > work would be very useful for real world java and clojure running in > "embedded java" whether it be a DVR glitching-out due to an improbable > concurrence, or hospital life-support equipment, or aircraft control, > military control, etc. > Seems like this could also be a good potential "marketing opportunity" for > Clojure, were it to be used as the basis for building provably-correct apps > that run in a JVM. I think that market is much bigger than the "provable > microkernel in C" market. E.g. toolkit for building probably secure and > reliable cell-phone/multimedia java apps, or toolkit for building embedded > controller software on which people's lives depend, literally....
I'm pretty sure others will answer and elaborate with more background than I have, but here we go: What they are talking about is (semi) automated theorem proving [1] (subfield of automated reasoning). To do that you need to have a modeling language with very strict semantics, because you can only prove if you can 'reason' (make a guarantee based on certain assumptions) in an way about what a 'sentence' of your model language says. Very strict semantics with possibility to reason about it without actually running the program translates in the field of computer programming languages to static type systems. And here be sure to notice that the Haskell (static) type system is a couple of orders of magnitude more capable than the (static) type system of Java. I don't know where you would want to use Java and/or Clojure, but I doubt that you can get very far, because Java's static type system is too limited, and Clojure is dynamically typed. I think a functional language is easier to reason about compared to an object oriented one (please someone comment on this), but it's not enough for theorem proving. The documentation available in HTML on the site is a bit thin as to how they actually used Haskell and C together, check the paper: "seL4: Formal verification of an OS kernel" [2]. The actual implementation and what they prove (and not prove) can be found in section 2 - Overview. Cheers, Daniel [1] http://en.wikipedia.org/wiki/Automated_theorem_proving [2] http://ertos.nicta.com.au/publications/papers/Klein_EHACDEEKNSTW_09.pdf > http://ertos.nicta.com.au/research/l4.verified/ and http://ertos.nicta.com.au/research/l4.verified/approach.pml >> >> The L4.verified project >> >> A Formally Correct Operating System Kernel > > In current software practice it is widely accepted that software will always > have problems and that we will just have to live with the fact that it may > crash at the worst possible moment: You might be on a deadline. Or, much > scarier, you might be on a plane and there's a problem with the board > computer. > > Now think what we constantly want from software: more features, better > performance, cheaper prices. And we want it everywhere: in mobile phones, > cars, planes, critical infrastructure, defense systems. > > What do we get? Mobile phones that can be hacked by SMS. Cars that have more > software problems than mechanical ones. Planes where computer problems have > lead to serious incidents. Computer viruses spreading through critical > infrastructure control systems and defense systems. And we think "See, it > happens to everybody." > > It does not have to be that way. Imagine your company is commissioning a new > vending software. Imagine you write down in a contract precisely what the > software is supposed to do. And then — it does. Always. And the developers > can prove it to you — with an actual mathematical machine-checked proof. > > Of course, the issue of software security and reliability is bigger than > just the software itself and involves more than developers making > implementation mistakes. In the contract, you might have said something you > didn't mean (if you are in a relationship, you might have come across that > problem). Or you might have meant something you didn't say and the proof is > therefore based on assumptions that don't apply to your situation. Or you > haven't thought of everything you need (ever went shopping?). In these > cases, there will still be problems, but at least you know where the problem > is not: with the developers. Eliminating the whole issue of implementation > mistakes would be a huge step towards more reliable and more secure systems. > > Sounds like science fiction? > > The L4.verified project demonstrates that such contracts and proofs can be > done for real-world software. Software of limited size, but real and > critical. > > We chose an operating system kernel to demonstrate this: seL4. It is a > small, 3rd generation high-performance microkernel with about 8,700 lines of > C code. Such microkernels are the critical core component of modern embedded > systems architectures. They are the piece of software that has the most > privileged access to hardware and regulates access to that hardware for the > rest of the system. If you have a modern smart-phone, your phone might be > running a microkernel quite similar to seL4: OKL4 from Open Kernel Labs. > > We prove that seL4 implements its contract: an abstract, mathematical > specification of what it is supposed to do. > > Current status: completed successfully. > > More information: > > What we prove and what we assume (high level, some technical background > assumed) > > Statistics (sizes, numbers, lines of code) > > Questions and answers (high-level, some technical background assumed) > > Verification approach (for technical audience) > > Scientific publications (for experts) > > Acknowledgements and team > > What does a formal proof look like? [pdf] > > Niels > http://nielsmayer.com > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. 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